This invention relates to methods of operating a station in a computer network; and more particularly it relates to methods of initializing a station and enabling a station to recover from hardware failures in such network.
Each station in a computer network typically has two sets of paired input and output terminals. These are normally coupled to respective paired sets of terminals of other stations on the network. Thus, if the coupling between stations is not broken and all the stations are operable, messages can be sent from any first station to any second station in the network by serially passing the message over the interstation coupling and through all of the stations which lie between the first and second stations.
A tutorial explanation of the many different aspects of computer networks is provided in the text Computer Networks and Their Protocols by D. W. Davies et al, published 1979 by John Wiley & Sons. Additional information is provided in the text entitled Computer Networks by Andrew S. Tanenbaum, published 1981 by Prentice-Hall, Inc. These texts describe, for example, various computer network topologies and protocols for routing messages from one station on the network to another. All of their teachings are herein incorporated by reference.
One problem, however, which exists in computer networks of the prior art occurs when a station or the coupling between stations becomes broken. When that occurs, messages cannot be passed from one station to another through the broken station or coupling. Thus a method is needed for rerouting messages through only those stations and interstation couplings which are operable. Otherwise, a single broken station or broken coupling in a network of many stations would render the entire network inoperable.
Also, when a broken station or broken coupling between stations is repaired, a method is needed for sensing such occurrence and for again rerouting the flow of the messages through the network such that the repaired stations and couplings are included in the message flow.
A similar problem occurs when all the stations of a network are initially powered down; and subsequently the stations are powered on one at a time in a random sequence. Here a method is needed for continuously sensing which stations and interstation couplings are operable, and for continuously rerouting the flow of messages through the operable ones as they increase in number.
Accordingly, a primary object of the invention is to provide a method of operating a station in a communication network such that it determines whether or not another station to which it is coupled plus the coupling itself is operable, and in response thereto causes internal message rerouting actions to occur such that messages can be sent through itself to the other station.